A huge market exists for disk drives for mass-market computing devices such as desktop computers and laptop computers, as well as small form factor (SFF) disk drives for use in mobile computing devices (e.g. personal digital assistants (PDAs), cell-phones, digital cameras, etc.). To be competitive, a disk drive should be relatively inexpensive and provide substantial capacity, rapid access to data, and reliable performance.
Disk drives typically employ a moveable head actuator to frequently access large amounts of data stored on a disk. One example of a disk drive is a hard disk drive. A conventional hard disk drive has a head disk assembly (“HDA”) including at least one magnetic disk (“disk”), a spindle motor for rapidly rotating the disk, and a head stack assembly (“HSA”) that includes a head gimbal assembly (HGA) with a moveable transducer head for reading and writing data. The HSA forms part of a servo control system that positions the moveable transducer head over a particular track on the disk to read or write information from and to that track, respectively.
Typically, a conventional hard disk drive includes one or more disks wherein each disk includes a plurality of concentric tracks. Each surface of each disk conventionally contains a plurality of concentric data tracks angularly divided into a plurality of data sectors. In addition, special servo information may be provided on each disk to determine the position of the moveable transducer head. The moveable transducer head typically includes a writer and a reader.
The most popular form of servo is called “embedded servo” wherein the servo information is written in a plurality of servo wedges that are angularly spaced from one another and are interspersed between and within data sectors around each track of each disk. Each servo wedge typically includes at least a phase locked loop (PLL) field, a servo sync mark (SSM) field, a track identification (TKID) field, a sector ID field having a sector ID number to identify the sector, and a group of servo bursts (e.g. an alternating pattern of magnetic transitions) that the servo control system of the disk drive samples to align the moveable transducer head with or relative to a particular track. Typically, the servo control system moves the transducer head toward a desired track during a “seek” mode using the TKID field as a control input. Once the moveable transducer head is generally over the desired track, the servo control system uses the servo bursts to keep the moveable transducer head over that track in a “track follow” mode.
During disk drive manufacturing, the disk of the disk drive is scanned to detect defects that are present on the disk. A log is generated to indicate the locations of the defects detected on the disk. The log typically has a finite size. If the log becomes full before the entire surface of the disk is scanned, the disk drive fails the manufacturing process.
The presently-utilized disk drive manufacturing process that fails the disk drive when the finite sized log becomes full unfortunately fails disk drives that are actually capable of passing the manufacturing process. This is because, oftentimes, the continued scanning of the remaining surface of the disk may yield fewer defects such that the disk can still be formatted to achieve the targeted storage capacity for the disk of the disk drive.
Therefore, there is a need in the disk drive manufacturing process to enable further scanning of the disk and to not fail a disk drive based solely on an overflowing log.